XtAppAddActionHook adds the specified
procedure to the front of a list maintained in the application context.
In the future, when an action routine is about to be invoked for any widget
in this application context, either through the translation manager or
via XtCallActionProc, the action hohok procedures will be called in reverse
order of registration jut prior to invoking the action routine.

Action hook
procedures are removed automatically and the XtActionHookId s destroyed
when the application context in which they were added is destroyed.

XtRemoveActionHook
removes the specified action hook procedure from the list in which it
was registered.